The use of intravascular catheters has become an effective method for treating many types of vascular disease. In general an intravascular catheter is inserted into the vascular system of the patient and navigated through the vasculature to a desired target site. Using this method, virtually any target site in the patient's vascular system may be accessed, including the coronary, cerebral, and peripheral vasculature. Examples of therapeutic purposes for intravascular catheters include percutaneous transluminal angioplasty (PTA) and percutaneous transluminal coronary angioplasty (PTCA).
Catheters are also known for use in other body lumens for non-vascular therapeutic purposes. These can include pancreato-biliary treatments and urological applications.
Generally, a catheter enables a physician to remotely perform a medical procedure by inserting the catheter into a body lumen, such as a blood vessel, of a patient at a location that is easily accessible, and thereafter navigating the catheter to the desired target site. By this method, virtually any target site, whether in the patient's vascular or non-vascular lumen, may be remotely accessed. In vascular applications, the catheter typically enters the patient's vasculature at a convenient location such as a blood vessel in the arm, neck or near the groin. In both vascular and non-vascular applications, the path taken by the catheter through the body lumen is generally tortuous, requiring the catheter to change direction frequently. It may also be necessary for the catheter to double back on itself. Physicians often apply torsional forces to the proximal portion of the catheter to aid in steering the catheter. To facilitate the steering process, it is desirable that an intravascular catheter have a relatively high level of torqueability. Furthermore, in order for the catheter to conform to a patient's tortuous anatomy, it is desirable that the catheter be relatively flexible. The requirement that the catheter include a relatively high level of torqueability and yet remain flexible is at times a competing requirement, as increasing wall thickness of a catheter shaft tends to increase torqueability while compromising flexibility.
Guide catheters are one type of catheter used in both vascular and non-vascular procedures to aid in delivering other catheters or other interventional medical devices to a treatment site in a vessel or other lumen within the body. In a routine coronary angioplasty procedure, a guiding catheter is introduced into a peripheral artery and advanced over a guidewire through the aorta until the distal end of the guide catheter is engaged with the appropriate coronary ostium. Next, a balloon dilatation catheter is introduced over the guidewire and through the guide catheter. The guidewire is advanced past the distal end of the catheter within the lumen of the diseased vessel and manipulated across the region of the stenosis. The balloon dilatation catheter is then advanced past the distal end of the guide catheter over the guidewire until the balloon is positioned across the treatment site. After the balloon is inflated to dilate the blood vessel in the region of the treatment site, the guidewire, balloon dilatation catheter and guide catheter can be withdrawn.
Likewise, angiographic catheters can be used in evaluating the progress of coronary artery disease in patients. Angiography procedures are used to view the patency of selected blood vessels. In carrying out this procedure, a diagnostic catheter having a desired distal end curvature may be advanced over a guidewire through the vascular system of the patient until the distal end of the catheter is steered into the particular coronary artery to be examined. Diagnostic catheters are also used in non-vascular procedures to assess disease state.
Balloon catheters used with the above-described guide catheters are typically classified as over-the-wire (OTW) or single operator exchange (SOE). An OTW catheter includes a guidewire lumen extending through a tubular shaft from the distal tip of the catheter to the proximal end of the catheter. A second tubular shaft extends coaxially over the first shaft to form an annular inflation lumen therebetween in fluid communication with a balloon disposed near the distal end of the two shafts.
SOE catheters have a relatively short guidewire lumen relative to the length of the catheter which extends through a first tubular shaft. The first tubular shaft is usually disposed within a lumen of a second tubular shaft which extends the length of the catheter. The second tubular shaft lumen again provides means for inflating the balloon disposed near the distal end of the shaft assembly.
A common feature to all catheters is the need for shaft assemblies which have adequate torque transmission and yet retain sufficient flexibility to reach desired treatment sites. Tubular members having lumens therethrough are generally used to form the shaft assemblies and selection and design of the tubular members determines the resulting balance between torqueability and flexibility.